Saturday, December 19, 2015

FAQ-4 How do power banks work?

Good evening everyone, as a continuation of this frequently asked question post I will be writing about something pretty new, interesting and helpful too. I wrote about how to make this device but I think it is better to write another separate one just giving the idea of how it works, so here it is how power banks or portable mobile/laptop chargers work.


Before jumping into how it does what it does, let's see what it does. Power bank is essentially a small portable device that stores energy and provides you with that while on the go. Usually most small power banks provide 5V on an USB port so it is very convenient to charge any mobile device although fast charging might not be available on most of them but it will get the job done. Most of them provides about 1A of current some can give 2.1A of current, depending on the model. There are however some slightly larger ones that has the ability to power small laptops too, they usually can store more energy so that they can provide more energy. That's pretty much what they do.

Picture taken from Internet

To understand things a bit better, let's take a look at a block diagram of how these devices work, after that we will see some of the major and minor components of it. 


Major components:

Moving on to the main question, how does it work? To my knowledge all of these devices use Lithium Ion/Lithium Polymer battery as their power source, so in the inside they have these type of batteries, remember this is the same type of battery that is inside of your phone, tablet, laptop or most of the portable devices that we use these days. These cells are so popular and widespread due to their high weight to power ratio, Lithium batteries can provide about 300W per kg where the other ever popular lead acid can only do 180W per kg. So more power, less weight that's what is needed on a portable device.

So we have got the battery for such devices, lithium ion or polymer, now we need to make sure it can provide proper voltage and current to the device. Lithium cells has a nominal voltage of 3.7V and can go all the up to 4.2V while fully charged, but the USB ports that we use has 5V with strict regulation. So we need to change this cell voltage to 5V. How can it be done? Usually it is done by a boost converter that provides a steady 5V on its output regardless of the battery voltage being at 3.7V or 4.2V or anything in between them. If more than one cell is used, what I have seen is manufacturer uses them in parallel, so they can use the same circuit just have better service time. Although the one that I made, I used two 18650 cells in series and use a buck converter to lower the voltage to 5V. Either way output voltage is 5V, we got it on USB so we can charge any device. Another important thing about this boost converter is, it usually limits the output current too, depending on the circuit it can provide different amount of current. In some cases, where it is suppose to charge a laptop however, the output voltage can be 12V or 19V depending on the model or depending on the device that it's manufacturer is aiming at. So we have a power source inside and a circuit that can provide our desired voltage and current, everything is fine so far but we need to charge this cell right?

So next part, charging the battery that is inside of them. Charging a lithium ion is a bit tricky. You have to make sure to put proper voltage and current in and change the charging profile when necessary and you have to control the voltage otherwise it can blow up! Lithium ion takes a steady/constant current up until they reach their 60-70% capacity then it charges at a constant voltage, steadily declining the input current to them. So you need a charging circuit that have such ability. Also it is safe to use a charging current that is half of it's amp-hour rating. For smaller capacity power banks, usually an USB input is provided for charging it up, as smaller capacity devices have smaller cells it is easy to top them up with a smaller current from any USB port. Larger capacity ones however include their own power brick or AC adapter with them to charge it from AC main line.

Now we have a working power bank that can take in power from USB or an AC adapter(similar one that is found with any phone, tablet or laptop, but might have a different output voltage) and charge a battery inside it and can power your device using that stored energy. Done? Not really, there are some more bits and pieces of stuffs in their. Let's talk about them.

Minor components:

Usually these devices, or at-least the good ones have indicator that shows the battery percentage, so you can see how much power it has left or should you charge it or not. So we need a circuit that can sense the battery capacity and show us by maybe a multi-color LED or maybe a bar graph or maybe with a LCD. This circuit will also tell us when it is fully charged so we can unplug it. Some of these devices have some built in meters for measuring voltage and current, usually on the output section and they use LCD or LED display to show that. Some more advanced ones can even show how much time left for it to power the load that is connected to it. Without these circuits, the power bank will still work but they make stuffs a lot easier and more suitable for using.

There are some more circuit to ensure the safety of these devices, like temperature sensor or current sensor. What it does is while charging or supplying a load it keeps on checking the battery or the circuit temperature to ensure that both of them are within their standard operating range, if something goes sideways it automatically turns itself off. They also measure output current too to see if the output current is within it's limit, if not, it will automatically turn off. Another protection circuit is there to protect the battery from going below a certain voltage level, some battery has this protection built in but if it doesn't have that circuit it might be added to the design to ensure good health of the battery.

This is pretty much how power banks work, but all the circuit blocks that I have mentioned here might not be available in many designs but reputed manufacturer will have them for sure. There are huge amount of power banks available with many different capacities and it is pretty overwhelming in most cases to select the perfect one. Yet simple advice go for the reputed manufacturer or the one with better warranty policy. Some power banks might come with torch light too, get them if you find it necessary.

Some power banks might have wireless or induction charging that uses different circuitry to make magnetic field to transfer power, This post is already kind of long so won't get into details. 

More questions:

Q1: Capacity that is printed on these devices, is that true or false?

A1: Usually they lie about the capacity, you will see a lot of very small and thing 20k-30k mAHr rated power banks that are very cheap, open them up you will be greeted with maybe 4k-6k mAHr rated cell inside. With those cells there is no possible way for them to provide that much power. Cost is another thing, lithium ion is not cheap, so no one can just shove huge amount of power in those power banks without increasing the cost.

Q2: How can I know if my power bank has proper rating or not?

A2: If it is from a reputed brand, probably it is telling you the truth, if not it might not be true. You can always open up the power bank to see and test the actual battery or just charge it from 0 to 100% by using a known source, if a 20k mAHr power bank fully charge within 3 hours via a 500mA USB port, you know it is fake.

Q3: Charging phone or tablet using these power banks, how safe it is?

A3: It is safe, as long as it is providing proper voltage and adequate current with least amount of noise, it will be fine. There is a lithium ion charging circuit inside of the phone too, the same or similar one that is inside of the power bank, and it will take care of that 5V power and usually reputed manufacturer's power banks are safe to use.

Q:4 If I connect the output of it to the input of it will it keep on charging itself for infinite amount of time?

A4: No, these circuits make heat, so they waste power and for that the lithium battery will be depleted after some time.

Q5: Which one is best for me?

A5: Ask yourself, what kind of device you are planning to charge, how many times are you planning to charge, what form factor suit you best. After getting all those answers you will know what to buy. If you want to charge a tablet with a 4000mAHr battery, there is no point buying a 3000mAHr power bank, because you won't even be able to charge once, but hey if form factor is the issue, go ahead and buy, you will still be able to get some.

I think that answers most questions that I found on the internet and in real world if you have any more question feel free to ask.


1. Boost Converter.
2. Lithium Ion Battery Charging.
3. Battery Capacity.
4. How chargers work.
5. Making a portable charger or power bank.
6. My other posts.
7. Inductive Charging.

Saturday, December 5, 2015

FAQ-3 Random Question About Incandescent Light Bulb

Do you know there is an incandescent light bulb that is on for about 114 years? Sounds weird right! Because most of the similar lamps that we use usually dies within couple hundred to thousand hours of service, but this light bulb at California, USA is actually here for about this time. Anyway good evening everyone this post will be about as you have already guessed Incandescent lamp.

Incandescent light probably is the oldest type of electrical light bulb and it is here for a pretty long time now, although they are kinda at the end of their prime but they are still used in many different places where heat is needed as this light bulbs are very inefficient, they puts out huge amount of heat and also in places where cheap lighting solution is needed. Anyway maybe will post some more on to this topic later, for now let's look at the questions.

Q1. Why does incandescent light bulb damages mostly during they turn on?

Well it is a very interesting question, you will see that this type of lights usually burns out while you switch them on, yes they do get damaged during service but what I have seen and pretty sure many other people have seen, they tend to get damaged while the turn on process. To understand why we have to know how this light bulbs actually work. Incandescent lamps are probably the simplest thing to understand, the only thing they have is a filament in either vacuum or inert gas filled glass structure. This metal filament (mostly tungsten) is coiled and is attached to two metal connector which provides the electrical connection. Whenever you put it in a power source the voltage across this filament pushes current through it, and pushing current through a wire with resistance makes it hot and starts glowing, hence we get the light. Now why it is covered in the glass? Mostly because if it was open it would have oxidized pretty easily and burn out the filament in seconds so the glass chamber and it is vacuum. Although vacuum can get rid of the oxidization problem but while the light is on, the metal filament starts to evaporate, hence lowering the strength of the filament and eventually leading to failure. To prevent this inert gas is introduced at 0.7 atmospheric pressure which redeposit the evaporated metal on to the filament again and increasing life span of the lamp. Yet none of this is 100% accurate so lamps do get damaged over time, the filament gets weak.

So back to the original question, you see when the lamp is first turned on the metal filament is cold and we know cold metal have less resistance than hot metal, so during the first turn on the lamp allows a high amount of current through it but as soon as the filament heats up the resistance starts to increase thus decreasing the current through it. Consider this, a incandescent lamp is on and it is taking in a certain amount of current and with time the filament is getting weaker, but okay for the amount of current it is carrying during the comparatively high resistance hot filament state but you have turned it off after say a 20 hour service and the filament is weaker than before, so when you turn on next time the amount of current can be such that it blows the filament, so this is what usually happens and we see that incandescent lamps got damaged mostly while being turned on.

Q2. What is the life span of a normal incandescent lamp?

About 1000 hours, but there is more to this question, actually incandescent lamps have much greater life-span but manufacturers intentionally lowers that to 1000 hours to make more sale. This is a very interesting story,will put a link below.

Q3. What is the efficiency of this type of lamps?

About 10% at best, if you need light. If you need heat, well then the efficiency is much higher.

Q4. What type of load is a incandescent lamp is?

Like I said earlier it can be treated as a resistor so it is a purely resistor based element which means it has a power factor of 1 and it can be used on AC or DC without any problem.

So anyway I don't actually have any more frequently asked question about this topic but if you have any please do let me know and this incandescent lamp was an enormous innovation to be honest, you know what people say about them? "The most profound invention since man-made fire", they served us pretty well and still serving us, they are clean, cheap and easy to work with but due to their lack of efficiency many countries are banning them or replacing them but no matter what people will never forget these lamps for sure.


The incandescent lamp that is on for about 114 years! 

So I was talking about manufacturers limiting the life-span to 1000 hours, here take a look at this article.

Want to know more about incandescent lamp? Read this!

Interested in reading some more? Here, visit the index page of my blog!

Picture is taken from internet.

Have a great day! 

Wednesday, October 28, 2015

FAQ-2 How does mobile phone or Laptop charger Work?

Again good evening and welcome back, in this Frequently asked question post I will try to answer questions that are asked by people very often so here is another post and this one is about how mobile phone and laptop chargers work.

Laptop and mobile phone charges are something  that we use everyday and they have improved a lot over the last couple years and main improvements include cleaner power and higher efficiency. Almost all of these chargers that we see today have switched mode design and they don't use line frequency transformer which makes it possible to be small in size but pretty powerful. So let's take an example and break it down how it works. In this particular post I will be talking mainly about a mobile phone charger but laptop chargers or even computer power supplies are pretty much the same these days, they utilize same technology.

So, in the picture what you see is a charger provided with the Asus Nexus 7 2013 tablet, this same charger is also provided with their first generation of Zenfone too.

So how does it work? Well first let's talk about input and output. If we look closely we can see that the

Input here is 100-240V AC 0.25A 50-60Hz, so it is global, which means it will work anywhere in the world as you might know some countries use 100-120V 60Hz and some other countries use 220-240V 50Hz in their household.
Let's take a look at the Output now, which is 5.2V 1.35A DC so you can pretty much charge any phone with it, time might vary according to that phone's battery and charging circuit.

So this wall charger is taking in 100-240V AC and converting it to 5.2V DC. Our question is How?

Well first stop,it takes in the AC voltage via the two prongs and then Converts the AC voltage to DC voltage with normal diodes.

Then the high voltage DC is filtered with capacitor, usually electrolytic type and capacitance depends on the power of the charger. It lowers the ripple voltage too.

Next this high voltage DC is fed into a circuit that converts it to a very high frequency and high voltage AC using components like integrated circuit, MOSFETs etc. The frequency of this AC voltage is about couple hundred kilohertz.

Then that high frequency high voltage AC drives a transformer (As the transformer of this charger is using very high frequency it doesn't need to be bulky).

On the other side or the secondary side of the transformer we get low voltage high frequency AC.
That AC is converted to DC via diode but not normal one, this time a schottky barrier diode. The reason for using this type of diode is mainly because it has to make sure that the conversion of AC to DC is good because normal diodes don't work that great with such high frequency.

Then again it is filtered with more capacitors, this time low ESR capacitor. ESR stands for equivalent series resistance, with lower resistance more AC component can flow through it which ensures that even if there is some of the high frequency harmonics available after the final conversion, it will be omitted. These capacitors also lowers the voltage ripple and keeps the voltage stable.

Hence we get the low voltage rectified DC which in this case 5.2V.

There are other things inside of these type of chargers like the output is monitored and a feedback is given to the High voltage DC to high voltage high frequency AC circuit to make sure that the voltage stays stable. Usually with low current consumption voltage tends to rise and this information is sent to the control unit which usually lowers the frequency of switching or the duty cycle to keep the voltage low as well and vice versa.

There might be some temperature sensors too, if the temperature goes beyond a specific value it might turn off automatically. 

There are also some X and Y capacitors for safety reasons. And there are some other capacitor to suppress the noise from AC main line.

This is how most modern laptop and mobile chargers work although there are some newer chargers that are "smart" as well. Smart in a sense that it can sense the device connected to it and might change the power profile. For example the new Asus Zenfone comes with a charger that can deliver 5.2V 1.35A DC in normal condition but if you connect it to a phone that can take up high amount of power it can deliver 9V 2A so in normal case it can deliver around 7W and in special case it can deliver 18W which helps the phone to charge their batteries faster. New Samsung phone also have this type of charger. So in this case there is some added circuitry in the charger that allows the charger to communicate with the phone or laptop, new Lenovo laptops also has this option too and upon sensing this the charger changes the power profile and switch to a different power profile and provide that. This option allows the charger to be used with all standard devices and at the same time it makes it possible to utilize faster charging for specified devices.

This is how modern chargers for mobile, laptop or router work, they are not as simple as the linear ones mainly because they need to be more efficient and compact. 

If you want to read more about my posts just you can visit the index of my blog.

Index page.

Have a great day.

FAQ-1 Battery Capacity mAh, Ah, Wh

Good evening everyone, although it is about 3 a.m. but whatever I will be starting a new segment where I will try to answer questions that are often asked. So the first one is a bit about battery capacity. Many people ask me about it and I see many people ask someone else about it so I thought why not just try and answer it simply! So here it goes!


Let's talk about mAh first because you will see this unit very often. Your mobile phone's battery, laptop's battery or portable media player's battery might have this rating printed on it. So what does that mean? Well mAh has two parts one is the mA or Milli-ampere and the second part is hour so in total it means how much current can the battery provide for an hour. For example if you have a cell that has a rating of 1000mAh it means if you draw 1000mA from it it will last for an hour. Theoretically it also suggests that if you draw more, say 2000mA from it, it will just give you 30 minutes and if you draw less, say 500mA it will give you 2 hours. So, I said theoretically why? Because battery has internal resistance which can be realized as a resistor in series with a power source, so more current you draw more power will be wasted on the resistor as we know that power dissipated on the resistor is equal to the value of resistance multiplied by the square of the current that is flowing through it. So more current, more waste and that's the reason why batteries heat up with higher current draw. There is one more thing, as I said earlier a 1000mAh cell can deliver 1000mA for one hour, does that mean it can provide 60000mA/60A for a minute? No, not really. Why? Because as I said there is an internal resistance that can be assumed as a series resistance with the source, so it will limit the current and each battery chemistry and construction has it's limit so 1000mAh does not indicate it can provide 60000mA/60A for even a minute.


Next stop Ah, there is not much to say about it really because it is almost the same as mAh which you might have guessed. The reason for using this unit is sometimes for powerful batteries if you need to express it in mAh, the numerical digit might become huge for example if you think about a car battery it is much easier to write 100Ah rather than writing 100000mAh. So to make life a little easier this unit is used with batteries that has higher capacity. Even for slightly smaller cells too like a normal 1200VA computer UPS usually comes with two 7Ah battery.


So far I have talked about mAh and Ah which are used all over the world for understanding battery capacity but there is one more unit, Wh or Watt hour. Why do we need another one? Well let's break it down, this unit has two parts like the other two, one the Watt or unit of power and other being the hour or unit of time. So Wh will simply tell you how much power you can get out of a battery for one hour but why do we need that? Because the mAh/Ah doesn't give you any indication of power. Let's think about it, how much power can a 1000mAh battery provide? Sadly we can't answer that question because power is the product of voltage and current and in this case we don't know the voltage so we can not answer this question. Another problem is if someone ask you that are all 1000mAh battery the same? Again we don't know the Wh so we can not tell. Let's look at an example, say a NiMH cell has a capacity of 2000mAh and a lithium ion with the same capacity, 2000mAh, are they same? No because the lithium ion can deliver more power than the NiMH because lithium ion has a nominal voltage of 3.7V where the NiMH has 1.2V so the Lithium ion will have 7.4Wh as opposed to the 2.4Wh of the NiMH. Let's look at an interesting thing here, even if I assume the lithium ion to be of 1000mAh capacity, it will still have 3.7Wh rating where even with 2000mAh rating the NiMH has only 2.4Wh rating. So recently many devices comes with Wh rating too, like the Lenovo laptop that I'm using right now has a 54Wh battery.

Like mAh and Ah there is a smaller unit of Wh too, which is mWh essentially the similar thing and I guess you know the simple math already, 1000mWh is equal to 1Wh.

If you don't have the information about voltage say you only know about the mAh rating and type of the battery, can you determine the Wh rating? Yes in many cases you can. Let's look at the chart to understand this better.

The table itself is self explanatory I think, so if you know the battery type and mAh/Ah rating you can easily find the Wh rating using this table. There are many other types of batteries out there but these are the most common ones so to keep things simple I have only mentioned them.

If you want to learn more about this I would highly suggest you to check out the following links below which might help you clear a lot of confusions about this.

Wikipedia Link:

1. Ampere Hour
2. kilowatt Hour
3. Battery type Comparison

Quora Link:

1. Meaning of mAh

Youtube Link;

1. Ah and Wh rating.

If you are interested in more of my posts take a look at my other posts here.

About me and Index of my blog.

Hope You have enjoyed the post. Have a good day.

Saturday, September 19, 2015

Introduction to Computer - Hardware

Good morning everyone, it has been a very long time since I wrote anything so I think I should write something. How about basic computer parts? Good idea I guess! So let's begin.

Spoiler Alert: This will be a long post!

Here I will be focusing mainly on the desktop computers and will try to walk you through the basic hardware that is needed to build and run a system.


The very first thing that you will be needing here is the Processor and as the name suggests it is fairly easy to understand it's purpose, it will process something. In a single processor desktop environment, usually the processor does all the major calculations. This processor is actually the very heart of the CPU or central processing unit. So we will be needing a processor to build a computer. Right now the processors that we are using has multiple processing cores and small amount of very high speed internal memory. Each core is actually the unit of processing, more cores usually results in better multi-tasking which means doing many works simultaneously. As we often run more than couple programs at the same time it is better to have a multi-core processor. There is also another technique that makes the better utilization of CPU time, which is called multi-threading, which also allows greater multi-tasking capability. The small amount of memory that the processor have is used for storing the instructions and addresses. Usually this memory is the fastest memory of the whole computer. It is usually volatile type, just like the Main system memory or the RAM, so as long as computer looses power it also looses anything stored in here. This memory might be divided into multiple levels. About the clock speed that is advertised on the processor is the speed that the core/cores are running at. For the same processor higher clock speed usually results in better performance although the processor will burn more energy and will get more hot. For the same processor more cores usually results in more power consumption and higher temperature too. And if you are wondering yes you can turn cores on and off, multi-threading on and off or increase or decrease the clock speed if you have suitable processor and motherboard. So how does the processor tackle the heat? In desktop environment usually it is done by actively cooling the processor with a metal fin array that helps to increase the surface area and one or more fans to blow air through them in order to dissipate that heat. To make good contact between processor's heat spreader and the metal fins a thermal interface material is used, which seals two metals and thus allow heat to be transferred to the fins faster.

For demonstration purpose I'm using a core i7 2600 processor. To cool it down the cooler that I'm using is the Cooler Master 412S and the thermal interface material is the Thermaltake TG-2.

Processor on the motherboard : It is a Core i7- 2600 Processor with 4 Physical Cores but can act as 8 logical cores because of multi-threading, it has 8MB of Level-3 Cache Memory and a default Clock speed of 3.4GHz.

Thermal Interface Material being applied to the integrated heat spreader of the processor.
Cooler for the processor with two fans, one will push air through the fins and other will pull air. Mounting screws and back plate is also shown. The copper heat-pipes allow faster transfer of heat to the fins.

The thermal interface material that will seal between the processor's integrated heat spreader and the bottom part of the cooler which ensures proper transfer of heat.

So that was kind of a basic of processors, lets talk about which is needed for what. If someone wants to build a desktop just for media consumption, internet browsing, office works or for educational purpose a dual core processor will be enough for him/her. Or it can be stated like this, a 100US$ processor will be enough for this purpose. As I'm writing this right now, for around a hundred dollar a 4th generation Intel Core i3 processor or an AMD FX4350 can be found. Both of them are well suited for this job.
If anyone needs to play games on it then he will definitely need something better than this. He will also need a graphics card which I will talk about later. So here a Quad core processor will be enough for this. Or anyone can target at a 200-250US$ processor. At this point a core i5 4th generation/6th generation or AMD FX8370 is available at this price point which will suffice this.
Right now many people are using their desktop computers to do more than just gaming or daily usage, they use it for streaming or video editing. If you want to do this you have to go with something powerful yet if you don't want to spend that much you have to target at something that is more powerful than a quad core processor. A core i7 processor might come in handy. Sadly at upper tier AMD doesn't have that much of a powerful processor the FX-9590 is available although not as good as a Quad core i7 because Intel's architecture is superior than AMD right now.
Want more than that? Well Intel's octa-core i7 is also available but that will cost you about 1000US$.

That was the basic about processor, let's move on to the main system memory or the RAM. While the computer is running it keeps the running applications or part of it in the RAM so that processor can work with it, RAM is pretty fast, much faster than secondary storage or Hard disk drive or Solid State drive but much slower than the processor's cache memory. Processor can directly access the memory, and more memory usually results in faster speed because processor don't have to go to the disk to fetch information often, it can keep larger data in the system memory. Although insane amount of RAM with a low end processor won't do any good because in that case processor will be the limiting factor. Currently the highest performing RAM that is available right now is the DDR4 memory, although only two platforms supports that so it is pretty rare. DDR3 is still very good performer though.

Each of this sticks is a Transcend 4GB 1333MHz DDR3 CL9 module, four of them gives a total of 16GB

So how much memory do you need? Again for normal works 4GB 1333MHz will be enough, for gaming however 8GB 1600MHz will do good for now and if you want more than that, you will be better of with 16GB 1866MHz+. Although for DDR4,  the nominal speed is 2133MHz although that much of a speed is not needed in most cases.
Note: If you are rocking an AMD APU, better to get DDR3 2133MHz+ memory modules as the integrated Graphics shares the main system memory it is better to give them memory with higher bandwidth. Timing is also important on RAM, lower the value of it, better the performance is.

Next, the house that will house everything, the motherboard. It will allow you to put everything in there and connect all the peripherals. It houses the Processor and the RAM, it takes in the power from the power supply unit, convert it to power the CPU and the RAM properly. It also allow us to connect to the secondary storage such as hard disk drive/solid state drive/optical drive. It will also allow peripherals to be connected to it, like the network interface card, the sound card, graphics card, TV tuner card etc. It also has input output ports for connecting input devices like mouse or keyboard, monitor etc. There are some boards that won't allow you to connect a monitor to it by the way, in that case it is must to have a discrete graphics card. It also has USB ports to connect many different devices. There was a time when sound card and network interface card was to be bought separately and put it in the motherboard to get sound and to connect to a network, this days however good quality audio chip and network chip come with the motherboard thus allowing user have less hassle while building a system,

So this is the motherboard, it has RAM slots for installing the RAM, processor socket for the processor, Multiple Serial-ATA port for connecting Optical drive/hard drive/solid state drive, it has couple peripheral slot like the PCI slots and PCI express slots. It takes in power via two different port, the top 8pin EPS and the 24Pin port on the right. It has a battery to keep the clock going thus you don't have to set time each time you turn on the system. It has network interface card and sound card built into it.

There are so many motherboards out there in the market that will easily make someone confused, so what to look for? Well if you are looking for installing more RAM then definitely take one with four or more slots of RAM. Need more storage? grab one with more SATA ports, preferably SATA revision 3.0. You need to transfer stuffs on a regular basis take one with USB3.0 or higher. Need more GPU horsepower? take one that supports multiple GPU. Don't get caught up with the gimmicky marketing terms, try to understand what you need and take one accordingly.

So you definitely need power for this right? So you will need a power supply unit. I'm not going to write about power supply that much because I have already written about it. For demonstration purpose however I will be using a Corsair CX750 power supply unit.

The power supply unit: Corsair CX750
As you can see all the cables are visible here, those cables will be needed to power up all the components in your system.

Read this post to learn more about power supply unit.

If you want to play modern games however, you will need a decent Graphics card for this purpose. Many processors come with integrated graphics that will allow you to do most of the visual works but for graphically demanding task like gaming or GPU based rendering, you will need a discrete graphics card. Most graphics card this days will use the high speed PCI express port on the motherboard. If it has a consumption of more than 75W, you will have to put additional power plug to it which comes directly from the power supply unit.

A MSI GTX660OC 2GB Graphics Card
Integrated Graphics processor usually shares the main system memory or the RAM where the discrete card has its own high speed memory and also at the center of the card there will be a graphics processor. In the picture above the lower part is the PCI express interface that will allow us to connect it to a motherboard. The left side is where all the output ports are located, you can connect to monitor via those ports. The Graphics card however can get very hot so a fan and a heatsink is added by the card manufacturer to keep it cool.

If you are shopping for a graphics card ask yourself couple different questions like how many years are you going to play with it, how much money can you spend, do you want to add any other card later or the resolution and level of details that you are aiming for.  For one or two years, and a low budget with limited power and money you can take a look at the cards like Nvidia GTX750Ti/ Nvidia GTX950/AMD 270X/AMD 370, all of them will give good bang for the buck, letting you play games on full HD, you can use them for more than one year too but you might have to sacrifice quality a little to keep the game running in decent frame rate.
If you can spend more than that definitely look at the AMD R9 380 or the Nvidia GTX970, both will give you amazing performance and you can even go beyond full HD resolution.
Wants even better than that? Then save up and buy either one Nvidia GTX980Ti or Two AMD 390X, both will cost almost the same but two AMD 390X will give you very good performance and quality, even on 4k resolution, thanks to it's 8GB VRAM.

Let's talk about storage then, there are many different types of secondary storage available this days and mechanical hard drives are still being widely used due to the fact that they are fast enough and cost per gigabyte of storage is very low. Although this days people are getting solid states drives more often too mainly because they are fast. Current speed of SATA3.0 is about 6Gbps which is not enough in many cases in that case PCI Express based storage solutions are also used.

Different type of Storage solutions are shown in here. Now which one do you need? Well if you need faster boot time and faster application loading time, you can go with the SSD but for normal usage, HDD will do fine and best option will be combination of both of them, keeping Operating system and application on the SSD and media files on HDD you can store huge amount of media files and also have a fast system.

That is pretty much the basic hardware of a computer, you have to add in input output devices to work with it anyway.

Tuesday, February 17, 2015

Single Board Computers

Good evening everyone. This days increasing number of single board computers are seen in the market so it can be a bit confusing when selecting one. Hope this post will resolve some of those confusions by providing technical information and possible use case scenarios. While talking about single board computers the first that that comes to our mind is Raspberry Pi, so let's start with that!

Raspberry Pi 2 and Raspberry Pi 3.

Raspberry Pi 2

Raspberry Pi 3

I'm going to talk more about them together as they have many things in common and Raspberry Pi 2 still is relevant even being couple years old. So, let's start with the common things.

Common features:

4 USB 2.0 ports.
1 10/100Mbps Ethernet Port.
1 HDMI port that supports 1080p video.
1 TRRS AV port that supports composite video and stereo audio.
1 DSI for attaching display.
1 CSI for attaching camera.
40 GPIO pins.
Power provided by a Micro USB cable or GPIO pins.
1GB or RAM.
1 micro SD card slot.


RPi2: Broadcom BCM2836 System on Chip with 4 ARMv7 Cortex A7 cores running at 900MHz.
Video Core IV Graphics Processing Unit running at 250MHz. 
No Wi-Fi or Bluetooth.

RPi3: Broadcom BCM2837 System on Chip with 4 ARMv8 Cortex A53 cores running at 1200MHz.
Video Core IV Graphics Processing Unit running at 400MHz.
802.11n Wi-Fi and Bluetooth 4.1.

Short note on Raspberry Pi:

Raspberry pi is the most popular single board computer out there so you will get a lot of support which might make your project easy. In works like automation or media center Raspberry Pi is enough for handling it.
There are couple drawbacks however, it can't be used as a computer replacement because it is just too slow. For network attached storage the 100Mbps network will severely bottleneck the throughput.

Orange Pi Plus:

Saturday, January 24, 2015

Headphone Amplifier With TDA2822

Welcome back everyone, its been a long time since I was thinking about writing a headphone amplifier which is simple to built but has good functionality. So here it goes, a headphone amplifier that can be used in anywhere.

Sometimes we come across high impedance headphones like 600ohm or so. If anyone drive them with the built in sound card of a computer motherboard or try to run it from any other similar device he might not get that expected volume level. This amplifier could be a cheap solution for that problem. Also it can be a great project too.

In the very heart of this design we have the integrated circuit called the TDA2822. This chip is a low voltage power amplifier that comes in a small 8 lead Minidip package and got some excellent features such as

1. Supply voltage ranging from 1.8V to 15V, so very versatile and can be used in anywhere.
2. Low crossover distortion.
3. Low quiescent current (max 9mA), so you can keep it running without load for very long time.
4. Can be used both in Bridge tied load and stereo configuration.
5. Small packaging makes it ideal for compact designing.

Now lets take a look at the integrated circuit's pin configuration

Pin configuration of TDA2822

From the pin configuration it is pretty obvious that its diagram will be really simple. So let's dive in the stereo diagram first.

Stereo Configuration

The diagram is straightforward and simple. We have two inputs from a stereo audio jack, could be from anywhere from computer or mp3 player or any similar thing.

Input 100kohm variable resistors can be gang type and is used for controlling the volume.

You can add a input decoupling capacitor if you want. Could be 4.7uF or 10uF.

If the power supply does not come with its smoothing capacitor, you might need to add one with the supply voltage pin. Again could be anything from 10uF to 220uF or so.

Output decoupling capacitor can have less capacitance, circuit will still work but you may loose some bass response. Do not skip the 0.1uF non polar capacitor and the 4.7ohm resistor, these are used for the stability of the diagram.

Now if you need more power per channel, you can use this chip to design a bridge amplifier. Here is the diagram. 

Bridge Tied Load Configuration

As you can only the one input of this chip is used this time and the other is grounded, you can swap pins and the 10uF and 0.01uF capacitor with the pin 5 and pin 8, diagram should work just fine.

Again here nothing much to be said, you can add input decoupling capacitor here too, but no need of output capacitor this time.

Bridge mode will be significantly more powerful than the stereo. In stereo configuration you will get 300mW on a 32ohm load with 9V supply where in Bridge you will get 1000mW in similar condition. Worth mentioning with 10% distortion. 

Power supply for this.

As I was saying voltage supplied for this diagram can vary from 1.8V to 15V but lower the voltage will be, lower the output power will be. 

This circuit can be powered from almost anything, you can use an USB cable or single lithium ion cell to provide power, if you intend to use with low impedance headphones.

You can use another power supply using regulator chips like 7809 or 7812 if you want to use high impedance headphones or maybe you can use two or three lithium ion batteries in series.

Make sure not to let any noise from power supply enter the circuit. You can use this diagram too.

Power Supply For the diagram

Here 0.1uF capacitor is used for cancelling the noise from power supply. A simple transformer and a bridge rectifier can be used with this. Make sure to use proper grounding of the whole circuit to lower the noise.

So hope you enjoyed reading this post and hope you might give it a shot too. Happy experimenting!

Datasheet for TDA2822.
More about linear voltage regulation.
Using USB port power for powering other devices.
Index of my other posts.